Based on the traditional iterative algorithm, phase-only element was used to generate vortex beams with two Orbital Angular Momentum (OAM) modes in different energy ratios. The use of pure phase modulation results in the presence of undesired OAM modes in the vortex beams, which follow a pattern. Additionally, the number of initial input parameters in the iterative algorithm affects the energy ratio between the two OAM modes. By adjusting the number of initial input parameters, a more desirable relative power distribution can be achieved.
An experimental scheme based on interferometry is designed to measure the orbital angular momentum spectrum of vortex beam perturbed by turbulence. The orbital angular momentum spectrum of vortex beam can be calculated by using four light intensity images. The laser beam is modulated by a spatial light modulator to obtain a vortex beam, and then passes through another spatial light modulator loaded with a turbulent phase perturbation hologram to interfere with the reference beam. The orbital angular momentum spectrum of the vortex beam can be obtained by making use of two interference patterns and the intensity patterns of the vortex beam and the reference beam. The results show that the experimental scheme can measure the orbital angular momentum spectrum of the vortex beam affected by turbulence.
Aiming at the requirement of accurate simulation of near-space atmospheric infrared background radiation, this paper simulates near-space infrared atmospheric background radiance according to atmospheric parameters detected by satellites. The multi-channel infrared radiometer SABER (Sound of the Atmosphere using Broadband Emission Radiometry) carried by TIMED satellite (Thermosphere, Ionosphere Mesosphere Energetics and Dynamics) is used to acquire atmospheric profile. Combined with limb observation model and atmospheric background radiance calculation model, the transmittance and spectral radiance of infrared atmospheric background were simulated. The spectral radiance of atmospheric background under the standard atmospheric model and satellite atmospheric profiles was compared to analyze the difference between the two atmospheric parameter. In the infrared band, the atmospheric profile has a great impact on atmospheric background radiance. For the accurate simulation calculation of infrared background spectral radiance in different regions, the influence of atmospheric profile parameters should be taken into account.
In order to study the anti-turbulence performance of the perfect vortex beam which carrying Orbital angular momentum(OAM), the average intensity distribution, beam spreading and scintillation characteristics of the perfect vortex beam propagating in atmospheric turbulence are simulated based on the multi-phase screen method by making use of the Von Karman spectrum. The impacts of beam parameters (OAM number, wavelength,) and atmospheric turbulence parameters (inner scale, outer scale) on the beam spreading and scintillation of perfect vortex beams are investigated. The results show that the beam parameters can be adjusted to reduce the scintillation and beam spreading effects caused by atmospheric turbulence. Perfect vortex beams with smaller OAM numbers and larger wavelengths have better resistance to turbulence. The smaller the outer scale and the larger the inner scale of the atmospheric turbulence, the better propagation performance of perfect vortex beam. The research of this paper provides an important reference for optimizing the optical communication performance of perfect vortex beams in atmospheric turbulence.
The increasing significance of high-temperature gases in heat transfer, combustion, and rocket exhaust plume, restrictions motivate researchers to continuously seek more efficient and accurate models to explain the related physical phenomena. The traditional Curtis-Godson approximation (CGA) will lose accuracy in the presence of severely inhomogeneous participating combustion gases by ignoring the high sensitivity of the narrow-band halfwidth to gas temperature and pressure. In order to improve the accuracy of traditional CGA, this paper introduces a correction function to correct the narrow-band half-width along the line-of-sight direction of the combustion system, where the correction function is related to the thermodynamic state of the high-temperature gas. The infrared spectral transmissivities calculated by the line-by-line approach are used as the benchmark solution to evaluate the accuracy of our improved CGA. The results in this study can be used to efficiently calculate the radiative transfer of rocket exhaust plumes.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.